Balancing device



1932- c. o. MARSHALL 1,871,899

BALANCING DEVICE Filed Dec. 15, 1,924

Patented Aug. 16, 1932 UNITED STATES PATENT OFFHCE CHARLES ORR MARSHALL,OF TOLEDO, OHIO, ASSIGNOR TO THE WILLYS-OVERLAND COMPANY, OF TOLEDO,OHIO, A CORPORATION OF OHIO BALANCING DEVICE Application filed December13, 1924. Serial No. 755,638.

This invention relates to engines having pistons connected to crankshafts by means of angularly movable connecting rods, and particularlyto high speed multi-cylinder engines such as are used in automobiles,airplanes and motor trucks.

In engines of this type the upward movement of one or more of thepistons is approximately balanced by the downward movement of otherpistons, so that the cen-i ter of the combined mass of the pistons andtheir connecting rods remains in nearly the same position throughouttheir cycle of movement. Owing, however, to the angularp'osition assumedby the connecting rods as the crank arms swing about the crank shaftaxis, the pistons are pulled inwardly toward the crank shaft during thequarter revolution of the crank shaft moving them from the outer ends oftheir strokes, to positions in which their centers of mass are slightlynearer the crank shaft than their centers of stroke. During the sameperiod the pistons moving outwardly from the inner ends of their strokesdo not reach their centers of stroke. Because of this unequal oppositemovement of the pistons the center of the combined mass of thereciprocating parts moves slightly toward and away from the crank shafttwice during each crank shaft revolution. This unbalanced movement ofthe reciprocating parts is the cause of the so-called secondaryvibration of high speed multi-cylinder engines.

The principal object of this invention is to provide simple andeffective means for counter'ba-lancing the unbalanced movement of thereciprocating parts and thereby preventing the so-called secondaryvibration. I

Another object is to provide a counterbalance, the center of which movesso as to neutralize the movement of the combined center of mass of theparts.

Another object is to provide a counterbalance, the inertia of which actsupon the crank shaft to counteract the hammering efiect on the mainbearings due to the unbalanced movement of the center of the combinedmass of the pistons and connecting links.

Another object is to provide a counterbalance carried by the crank shaftand having a center movable to balance the movement of the center ofmass of the reciprocating parts.

Another object is to provide a counterbalance and means connected to themoving parts of an engine to so move the counterbalance as to neutralizethe movement of the combined center of mass of the pistons without theuse of intermediate gearing or linkage.

Another object is the provision of a counterbalance revoluble with thecrankshaft and means to move the counterbalance to neutralize themovement of the center of mass of the pistons.

Another object is the provision of a slidable weight and means on thecrank shaft for. imparting to the weight two outward and inward radialmovements during each revolution of the crank shaft.

Another object is the provision of a single weight with means on thecrank shaft for moving the weight to counterbalance the movement of thecombined center of mass of the reciprocating parts of the engine.

Another object is the provision of angularly movable members and meansconnecting them to the crank shaft to so move them 7 as tocounterbalance the movement of the combined center of mass of the otherparts of the engine.

Another object is the provision of angularly movable members connectedto the crank shaft and means for so moving them as to counteract thevibratory effect resulting from the angular movement of the connectingrods. j Y 7 Another object is the provision of angularly movable membersand means connecting them to the connecting rods for movement tocounteract the vibratory effect of the angular movement of theconnecting rods.

Another object is the provision of means for giving to an engine havingfour cylinders in line a dynamic balance similar to that of a doubleopposed. engine.

Another object is the provision of means for giving to an engine havingfour cylinders in line a dynamic balance similar to that of an enginehaving eight cylinders in line.

Other objects and advantages will be apparent from the followingdescription, in which reference is had to the accompanying drawingillustrating preferred embodiments of my invention.

In the drawing Figure I is a front elevational view of a four cylinderengine embodying my invention, parts being broken away and parts shownin section;

Figure II is an enlarged fragmentary side elevational view showing partof the engine illustrated in Figure I, some of the parts being shown invertical section on a plane through the axis of the crank shaft;

Figure III is an enlarged detail view of a counterbalancing weightshowing the means by which the weight is connected to the crank shaft,the crank shaft being shown in section;

Figure IV is a similar view showing the position of the weight after thecrank shaft has moved through a quarter revolution;

Referring to the drawing indetail, the engine illustrated is of the wellknown type commonly used in automobiles, having a frame 1 and aplurality of cylinders 2, the axes of which are vertical and parallel.Located beneath the cylinders 2 in a crank .1 case 3 and journaled inbearings 4; is a longitudinally extending crank shaft 5 having aplurality of cranks 6, one for each cylinder. In an engine of the typeillustrated, in which the number of cylinders is four, the cranksco-operating with the two end cylinders extend from the crank shaft inone direction, while the cranks co-operating with the two middlecylinders extend from the crank shaft in the opposite direction. Thepistons in the two end cylinders, therefore, move together in onedirection, while the pistons in the two middle cylinders move togetherin the opposite direction. When the cranks are vertical, one pairextending upwardly and the other downwardly, the pistons connectedrespectively to the upwardly and downwardly ex tending cranks are at theends of their strokes, one pair being at the upper end of the stroke,the other pair being at the lower end of the stroke. During thesucceeding quarter revolution of the crank shaft the crank arms swing:to horizontal position and one pair of pistons moves downwardly whilethe other moves upwardly. Owing to the angular position assumed by theconnecting rods when the cranks are horizontal, the pistons are not,however, at their centers of stroke when the crank arms are horizontal,but are all slightly below their centers of stroke, so that the centerof the combined mass of the pistons and tion of the crank shaft thecenter of mass moves upwardly to its original position and as the crankshaft swings through another 180 of its movement the center of massagain moves downwardly and upwardly. There are thus two down and upmovements of the center of the combined mass of the pistons andconnecting links for each revolution of the crank shaft. The distancewhich the center of the combined mass of the pistons and connectinglinks moves depends on the length of the connecting links and the lengthof the cranks and upon the distribution of the mass of thepiston-connecting link assemblies, but in most engines it is a verysmall fraction of an inch.

In order to neutralize-the vibratory effect produced by this rapidupward and downward movement of the center of the combined mass of thepistons. and connecting links, I have provided a counterbalance, thecenter of which moves oppositely, so that the center of the combinedmass of the reciprocating parts and the counterbalance remainssubstantially stationary.

As illustrated in Figures I to IV, the oppositely moving counterbalanceconsists of a weight 7, the center of mass of which is locatedsubstantially in the axis of a pin' 8 mounted by means of a block 9 andgroove 10 for vertical reciprocation beneath thecenter main bearing 4.of the crank shaft 5.

Formed upon or otherwise fixed to the center main bearing-4 is aneccentric boss 12, the axis of'which lies above the axis of the. crankshaft,and rotatably mounted upon the boss 12 is a bearing member in theform of a split ring 13 having two straight external sides 14. Slidablymounted upon the straight sides 14 and adapted to turn with the ring 13upon the boss 12 is a member 15, the outer periphery of which iscircular in form so that the member 15 may be rotatably journaled withina bearing ring 16 formed in the upper end of the counterbalance 7 Themember 15 is also provided with a pair of bearings 17 which slidablyreceive pins 18 that are fixed to the crank shaft 5 and extend therefromat right angles to the crank arms, so that when the crank arms arehorizontal the pins18 are vertical. The member 15 is thus so mountedthat it revolves with the crank shaft and'also moves radially thereto.By reference to Figure III it will be observed that when the pins 18 arevertical the center of curvature of the outer surface of the member 15,and hence the center of the bearing ring 16, is coincident with the axisof the stationary boss 12. In this position of the crank shaft theweight 7 is at its highest pointand' the center of mass of the combinedpistons and connecting links is at its lowest point.

Figure IV shows the position of the coimterbalance and counterbalancingoperating parts when the crank shaft has turned through a quarterrevolution. It will be observed that the center of the bearing ring 16has moved downwardly so that it lies in the axis of the crank shaft,which is below the axis of the boss 12. This downward movement isbrought about by the turning of the pins 18 to horizontal position andis permitted by reason of the fact that the member 15 is slidablymounted on the ring 13. When the counterbalance 7 is in its lowermostposition (the position in which it is shown in Figure IV), the center ofthe combined mass of the pistons and connecting links is in itsuppermost position. The counterbalance 7 moves upwardly and downwardlytwice during each revolution of the crank shaft, and the product of itsmass by the extent of its vertical movement may be made equal to theproduct of the combined mass of the pistons and connecting links by theextent of movement of the center of the combined mass. Since themovement of the counterbalance 7 is opposite to that of the center ofthe combined mass of the pistons and connecting links, the center of thecombined mass of the pistons and connecting links and the counterbalanceremains substantially stationary.

During the vertical movement of the member 15 it also swings laterally,but this lateral movement of the upper end of the weight is counteractedby the opposite lateral movement of the lower end of the weight and thecenter of mass of the weight which lies in the axis of the pin 8 movesvertically only.

The embodiments of my invention herein shown and described are to beregarded as illustrative only, and it is to be understood that theinvention is susceptible to variation, modification and change withinthe spirit and scope of the subjoined claim.

Having described my invention, I claim:

In an engine, in combination, a plurality of cylinders, pistonsreciprocally mounted in said cylinders, a crank shaft, connecting linksconnected to said pistons and said crank shaft, the arrangement beingsuch that the center of the combined mass of the pistons and connectinglinks has a vibratory movement, a weight, a bearing boss surroundingsaid crank shaft and having its axis parallel to the axis of said crankshaft and lying in the same vertical plane, a ring surrounding said bossand rotatable thereon, and a member slidably mounted on said ring andhaving a radially slidable connection with said crank shaft for movingsaid weight to neutralize the movement of the combined center of mass ofsaid pistons and connecting links.

CHARLES ORR MARSHALL.

